1. Field of the Invention
This invention relates to a method for automatic mass production and packaging of electrochemical cells, where cathodes and leaf anodes with attached terminals are carried on webs or adhesive tapes which are rolled onto spools. An insulating plastic net from a spool is placed in an electrolyte coater, unrolled, and the web is pulled through a tank where it is coated with a liquid polymer electrolyte, the electrolyte-coated net and a cathode web are joined, the assembly is solidified, and a top tape with leaf anodes is placed thereon, pressed together, and the assembly is cut between anodes to form single cell assemblies, which are stacked, heat sealed in a moisture proof metal foil bag and placed in a hard container. The method is also used to produce reversed assemblies of single cells where the anode is on the bottom and leafs of cathode are placed on adhesive tape on top of and are joined to the electrolyte. The leafs of anodes or cathodes are also optionally cut before assembly and in synchronized manner deposited on top of the electrolyte, and then covered by an adhesive top tape, to prevent accumulation of tolerances and misalignment.
This invention also relates to a similar but extended method for automatic mass production of bi-cells or bi-polar batteries where the top adhesive tape is omitted and
This invention also relates to a similar but extended method for automatic mass production of bi-cells or bi-polar batteries where the top adhesive tape is omitted and additional layers are added to form bi-cell assemblies and/or bi-polar electrochemical devices.
2. Description of the Prior Art
In the manufacture of electrochemical devices it is necessary to carefully control the quality and uniform thickness of the finished product. Electrochemical devices such as batteries and fuel cells, and particularly lithium metal batteries, consist of an assembly of at least a cathode layer, an electrolyte layer, an anode layer and terminals. The prior art devices often suffered from variable thickness, non-uniform composition or dispersion of chemicals, dendrite formation, shorting, and other quality control problems. The prior art manufacturing methods involved forming the cathode by extruding or extrusion-coating of cathode material on top of a current collector, and forming the electrolyte by extrusion coating of a polymer on top of the cathode material. The thickness and uniformity of both layers are difficult to control, and the width is limited.
My prior U.S. Pat. No. 5,443,602 describes apparatus for assembling single and bi-cell assemblies but with some applications does not operate satisfactorily to prevent stretching of the tapes and misalignment of the components.
The present invention uses a composite electrolyte construction of uniform thickness, and unlimited width. As the composite electrolyte has a web of insulating net embedded in ion-conductive polymer, the structure does not short, and is highly ion-conductive. The composite cathode of the invention has a net of carbon fibers, or other conductive fibers embedded in the cathodic material, and the current is collected from inside, which is more efficient. The structure is of uniform thickness, and unlimited width by nature of the process. The anode may have similar composite construction and benefits as the cathode, except that the electrically conductive fibers are embedded in an anodic material or a carbon matrix. In the present method, the short-comings of the prior art are overcome and many advantages are obtained.